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Well, ottos are fairly hard to keep alive. The goldies may or may not eat them, but it you still have that small tank, you have no more room for fish. Ottos are also tropical, goldfish are not.
I have 2 large goldie tanks with 4 over 8" fancies in each tank. The only thing I keep in with them is a couple Malaysian Trumpet snails and a couple mystery snails since they actually do better in the cooler water.
They could try especially if the goldies are good sized. You could try adding a few white cloud mountian minnows as a test for the oto's. Also I don't know if the oto's can tolerate the cooler temps.
Eventually the Goldfish will try to eat the Ottos. This puts your Goldfish at great risk as Ottos have spines and they will get stuck in the Goldie's mouth possibly causing major damage.